Using ‘I’ or ‘me’ depends on whether the pronoun [I or me] is acting as the subject or the object of the sentence. [The subject is what does the action; the object is what the action is done to.] ‘I’ can only be used as the subject of a sentence; ‘me’ can only be used as the object of a sentence. Ditto for she/her, he/him, we/us, etc.

Which of these sentences correctly use ‘I’ and ‘me’?

Harry and I will take the annual report to the meeting.

The winners of the contest were Morgan and I.

She called Harry and me on Saturday.

The argument was between Sally and me.

Andrew said, ‘Mother gave the keys to Elizabeth and me’.

All five sentences correctly use ‘I’ and ‘me’.

The first sentence is correct because ‘Harry and I’ are the subjects of the verb ‘will bring’. Much of the confusion with pronouns occurs in compound constructions. If we remove ‘Harry and’ from the sentence, we can easily hear which pronoun is correct: we would never say ‘Me will bring the annual report’.

Another instance in which the pronoun ‘I’ is correct is when we have a linking verb and need a predicate pronoun to rename the subject. Think of a linking verb as a mathematical equals mark: winners = Morgan and I. If both sides of the linking verb are equal, then we should be able to reverse the sentence and still have it make sense: ‘Morgan and I were the winners’ conveys the same meaning as ‘The winners were Morgan and I’. Since we would never say ‘Me was the winner’, neither should we say ‘The winner was me’. (Notice that once again it is easier to discern the correct pronoun if we get rid of the compound and focus on the ‘I’ or ‘me’ as if it were alone.)

The third sentence is correct because ‘called’ is an action verb, and ‘Harry and me’ are its direct objects: they are the ones who were called. It’s easy to hear that ‘me’ is correct in this construction if we remove ‘Harry and’: ‘She called me on Saturday’ sounds correct, while ‘She called I on Saturday’ obviously sounds wrong.

In the last two sentences, ‘me’ is correct because it serves as the object of the prepositions ‘between’ and ‘to’. As in every other case, simply removing the compound usually enables us to hear which pronoun is correct: we would never say ‘Mother gave the keys to I’.